Comparison of the in vitro activity of several cephalosporin antibiotics against gram-negative and gram-positive bacteria resistant to cephaloridine.

The in vitro activity of each of two oral [cefatrizine (BL-S640), cephalexin] and three parenteral (cefamandole, cefazolin, cephapirin) cephalosporin antibiotics was compared with that of cephalothin against 168 clinical isolates of gram-negative and gram-positive bacteria selected as resistant to 20 mug of cephaloridine per ml on the basis of agar dilution susceptibility test data. Each of the five other cephalosporins inhibited a greater percentage of gram-negative bacillary isolates than did cephalothin or cephaloridine, with minimal inhibitory concentration values ranging 2- to 50-fold lower. Significant differences between minimal inhibitory concentrations of the compounds tested were also observed in tests against strains of Streptococcus faecalis and of methicillin-resistant Staphylococcus aureus. Potential advantages of including more than a single cephalosporin antibiotic in the panel of antibiotics used for routine susceptibility testing, suggested by these observations, are discussed.